1. Field of the Invention
The invention relates to a reed relay which includes a tubular electrostatic shield between a reed switch and a coil.
2. Description of the Related Art
Reed relays are used for various applications and, in particular, in an IC tester, since the contacts thereof are sealed so that the reed relay is less effected by the environment.
With reference to FIG. 19, a conventional reed relay will be described below. The reed relay includes a coil assembly 100, a tubular electrostatic shield 118 which defines an axially extending central bore, and a reed switch 120. The coil assembly 100 includes a coil 106 provided on a coil bobbin of a resin material. The coil bobbin includes a tubular winding drum 104 which defines an axially extending central bore 108, and opposite end flanges 102. The electrostatic shield 118 is inserted into the central bore 108 of the coil bobbin, and the reed switch 120 is inserted into the central bore of the tubular electrostatic shield 118. The reed switch 120 includes a glass body 120 sealingly enclosing the contacts (not shown) which are connected to terminals 122.
The coil assembly 100 further includes a first pair of leads 110 connected to terminals 118a of the electrostatic shield 118, a second pair of leads 112 connected to the coil 106, a third pair of leads 114 connected to the terminals 122 of the reed switch 120. The first, the second and the third pairs of leads are connected to the corresponding external terminals by welding and are integrally formed with the reed relay by an insert molding method.
In the conventional reed relay, the electrostatic shield 118 must be inserted into the central bore 108 of the coil bobbin. This increases the number of the parts and steps of the manufacture. Further, the terminals 118a of the electrostatic shield 118 are manually connected to the first pair in leads 110, which results in increase of the manufacturing cost.
The conventional reed relay is not adapted for installation on a circuit board which includes a very large number of reed relays such as a circuit board for an IC tester, nor is it designed in consideration of the electromagnetic effect, on the reed switch of a first lead relay, of the coil of a second adjacent reed relay through the leads connected to the coil of the second relay, and the leads connected to the reed switch of the first relay.
Further, the conventional reed relay is provided with a package which is formed by an insert molding method. According to a prior art, a plurality of reed relays are respectively disposed in a molding form for the insert molding method. This reduces the manufacturing efficiency.